真空感应熔炼AerMet100超高强度钢脱氮实验研究

Experimental research on denitrification of AerMet100 ultra-high strength steel by vacuum induction melting

通过取样检测并结合热力学和动力学计算研究了氧化镁质(MgO)、镁铝尖晶石质(MgO·Al_(2)O_(3))和氧化钙质(CaO)3种坩埚和2种真空压力(50~100 Pa和5~10 Pa)对AerMet100超高强度钢脱氮的影响。实验结果表明:随着精炼时间增加,3种坩埚在2种真空压力下的钢液中N质量分数都逐渐减少。相比之下,CaO坩埚脱氮效果最佳,2种真空压力下30 min时N质量分数均减少到0.000 5%。动力学计算结果表明:MgO和MgO·Al_(2)O_(3)坩埚在2种真空压力下的钢液中O和S活度较高,脱氮反应均服从2级,即钢液脱氮受界面化学反应控制;而CaO坩埚在2种真空压力下的钢液中O和S活度较低,脱氮反应均服从1.5级,即钢液脱氮由液相边界层传质和界面化学反应共同控制。此外,减小真空压力,脱氮速率加快,有利于钢液脱氮。

The effects of three crucibles(magnesia(MgO), magnesia-alumina(MgO·Al_(2)O_(3)) and calcium oxide(CaO)) and two vacuum pressures(50-100 Pa and 5-10 Pa) on denitrification of AerMet100 ultra-high strength steel were studied by sampling detection, thermodynamic calculation and kinetic calculation. The experimental results indicate that the mass fraction of N in molten steel refined by three crucibles under two vacuum pressures gradually decreases with the increase of refining time. In contrast, CaO crucible has the best denitrification effect. The mass fraction of N in molten steel can be reduced to 0.000 5% at 30 min under two vacuum pressures. The kinetic calculation results demonstrate that the activities of O and S in molten steel refined by MgO and MgO·Al_(2)O_(3) crucibles under two vacuum pressures are higher. The denitrification reaction obeys the second order and the denitrification of molten steel is controlled by interfacial chemical reaction. However, the activities of O and S in molten steel refined by CaO crucible under two vacuum pressures are low. The denitrification reaction obeys the 1.5 th order and the denitrification of molten steel is controlled by interface chemical reaction and mass transfer of liquid boundary layer. In addition, the denitrification rate can be accelerated due to reducing vacuum pressure, which is beneficial to denitrification of molten steel.